The subject invention relates to a modular system for electrically interconnecting any number of printed circuit boards to a composite motherboard. More particularly, in digital computer systems, a motherboard is provided which serves as a common connection for transmitting signals to a plurality of printed circuit boards. The subject invention permits additional printed circuit boards to be readily added to the system without having to redesign components such as the power supply and cooling system as well as the motherboard itself.
The development of a new computer takes a significant period of time and is relatively costly. First, the internal circuitry must be designed based on the intended usage of the machine. Once the necessary circuitry has been formulated, a considerble amount of work is necessary to develop the proper configuration of the hardware components. For example, a plurality of printed circuit boards are designed carrying the components capable of performing the logic functions dictated by the circuitry.
In most systems, a motherboard or bus is provided which serves as a common connection for the printed circuit boards. In use, the motherboard is connected to the input/output system of the computer and functions to transmit signals between the I/O devices and each of the printed circuit boards. Accordingly, each of the printed circuits boards must be electronically interconnected to the motherboard.
In the prior art, the latter requirement limits the possible design configurations of the system. More specifically, when the unit is physically planned, all the printed circuit boards and the connected motherboard must be grouped in a particular location in the housing of the computer. In some situations this lack of design flexibility is a serious shortcoming. For example, when all of the printed circuit boards must be clustered in one area, problems associated with heat generation are increased. As can be appreciated, when many active components are situated in one location, large and complex cooling systems must be provided to prevent the overheating and breakdown of components.
Another shortcoming relates to the design configuration of the computer itself. For example, frequently a computer is developed to automate machinery. To permit convenient interfacing, it is often necessary to design the dimensions of the shell or housing of the computer to fit in a defined area associated with the machinery. Thus, the shape of the housing is dictated by its surroundings rather than by the functional requirements of its intelligence. In addition, the shape of the housing is a concern when designing small business and home computers since the appearance of the unit will affect its marketability. Thus, it would be desirable to reduce the design constraints imposed by the prior art printed circuit board and unitary motherboard combination, to permit greater flexibility in shaping the dimensions of the computer housing and the layout of the hardware.
Once the design of a computer has been completed, units are manufactured and distributed to customers. Typically, once the computer has been subject to a certain amount of field use, the manufacturer will receive various comments and suggestions for improvements which would make the device more attractive to consumers. Some of these suggestions merely require relatively minor modifications to the existing computer in order to implement the change. However, many of the suggestions relate to various functions which the system is either incapable of accomplishing or does not perform adequately.
To improve and expand the capabilities of the system, it often becomes necessary to design additional circuitry. Usually, the actual design work needed to devise the new circuitry, to provide an added function, is not extremely difficult or expensive. However, in order to incorporate the new circuitry in the computer, it is often necessary to completely redesign the internal hardware and support systems. More particularly, to provide enhanced computing power, it is frequently necessary to add additional printed circuit boards to the computer. In the prior art, this necessitated the redesign of the motherboard to accept the additional printed circuit boards. The latter requirement frequently proves too costly to justify its implementation. For example, in the initial design, the space in the housing provided for the motherboard and printed circuit board package may not have been sufficient to accommodate additional printed circuit boards. In addition, since the new printed circuit boards require added power, new, larger power supply systems must be designed. Further, since the additional printed circuit boards will generate heat, an improved cooling system must be provided. Accordingly, even though the circuitry needed to improve the system can be developed with relatively little cost, the addition of the circuits to the system can be prohibitively expensive. Therefore it would be desirable to provide a new and improved system which readily permits the addition of printed circuit boards to a computer when desired.